The present invention relates to the use of recombinant DNA techniques to produce heterodimeric human fertility hormones.
Various polypeptide chains have been expressed, via recombinant DNA technology, in host cells such as bacteria, yeast, and cultured mammalian cells. Fiddes, J. C. and Goodman, H. M. Nature, vol. 281, pp. 351-356 (1979) and Fiddes, J. C. and Goodman, H. M., Nature, vol. 286, pp. 684-687 (1980) describe the cloning of, respectively, the alpha and beta subunits of human choriogonadotropin (hCG).
Sugimoto U.S. Pat. Nos. 4,383,034, 4,383,035 and 4,383,036 describe processes for producing FSH, LH and hCG, respectively, in which human lymphoblastoid cells are implanted into a laboratory animal, harvested from the animal, and cultured in vitro; accumulated hormone is then harvested from the culture. This technique is not capable of producing substantially pure hormone free of any other human fertility hormone.
Cohen et al, U.S. Pat. No. 4,468,464 mentions the production of fertility hormones by recombinant DNA techniques. However, Cohen et al only uses a prokaryotic system which cannot produce biologically active human fertility hormone.
Pierce et al, Ann. Rev. Biochem., 50, 465-95 (1981) states that the alpha and beta subunits of LH are known to associate in vitro. The subunits referred to in this paper are obtained by dissociating naturally occurring dimeric hormone and allowing the units to reassociate. Such a disclosure does not permit the prediction that when synthesized by non-specialized cells transformed with recombinant DNA, the subunits would be properly glycosylated and folded for association so as to produce a biologically active hormone.
While many human proteins have been produced by recombinant DNA techniques the production of biologically active heterodimeric hormones by such techniques has not heretofore been accomplished. Heterodimeric fertility hormones are produced in the human body by highly specialized, differentiated cells which have evolved over a long period of time to carry out the specialized function of producing each particular hormone. The mechanism by which post-translational heterodimeric assembly occurs intracellularly in these differentiated cells is not known, but it is known that proper assembly is necessary for biological activity. Undifferentiated cells do not, as far as is known, normally produce hormones. Thus, whether or not a biologically active heterodimeric hormone could be produced in undifferentiated cells transformed with DNA encoding the alpha and beta subunits was totally unpredictable.